Means for regulating transmission circuits



Aug. 16, 1927. 1,638,952

H. NYQUIST MEANS FOR REGULATING TRANSMISSION CIRCUITS Filed Aug. 31.1922 2 Sheets-Sheet 1 0 V c o v v 0 J b 6 Z Z I 6 6' 7 9 .9 A l l J 5 JJ I N V EN TOR. 113i A TTORNEY 1,638,952 Aug. 16, 1927. H NYQUIST MEANSFOR REGULATING TRANSMISSION CIRCUITS Filed Aug. 31. 1922 2 Sheets-Sheer.2

IN V EN TOR. 17 flfylms'i BY flff y A TTORNEY communication line.

Patented Aug. 16, 1927.

UNITED STATES 1,638,952 PATENT OFFICE.

HARR Y NYQUIST, OF ELMHURST, NEW YORK, ASSIGN-OR 'IO AMERICAN TELEPHONEAND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

MEANS-FOR REGULATING TRANSMISSION CIRCUITS.

Application filed August 31, 1922. Serial No. 585,518.

This invention relates to means for regulating transmission circuits,and more especially the regulation of signaling lines, the regulationbeing introduced to compensate for changes in such lines due to varyinclimatic conditions.

Tleretofore use has been made of such regulation especially in longtelephone lines which carry a number of repeater stations. Usually apair of wires paralleling the communication line, such as a pair in acable, is set aside for the purpose of indicating the condition of theline over which transmission is to take place and which is to beregulated. On toll telephone lines, the most important climaticcondition which must be considered is that of temperature variations,which will produce an alteration in the attenuation ot' the line, and,where the lines are long and the resistance great, the effect of thisvariation may be quite substantial.

As an illustration of the use of such regulation and the means forobtaining it, reference may be made to United States patent to A. B.Clark, No. 1,438,219 dated December 12, 1922, which describes in detaila circuit arrangement in which the pair of wires used for indicating thecondition 0 the line, hereafter called the pilot wires, is made onebranch of a Wheatstone brid e. Fluctuations in the resistance of this piot Wire tend to unbalance the bridge and set into operation mechanismwhich will alter the gain due to a repeater installed in the It has notbeen considered, heretofore, economically feasible to introduce such aregulating mechanism at each repeater station, but ithas been thepractice to divide the line into regulator sections, each regulatorsection including several repeater stations. The regulating mechanism isthen installed at one of the repeaters on this regulator section,preferably one near the middle of the section, and

the total change in gain which should be introduced due to the changesover the whole regulator section is made at the one station, which maybe called the master station.

This system, as briefly described, has been a marked step in advance inthe art, but it may occur that communication is carried on between twostations lying between two master stations, and the section of the lineover which communication takes place does not include any regulatormechanism. On the other hand, the two stations between whichcommunication is to be carried" on may include a master station, but maynot be the whole or the equivalent of a regulator section to which itbelongs, and as a result there may be too much or too little re lation.Then, again, the concentration 0 the total regulation for a re latorsection at one repeater may intro uce a change so large as to overloadthe repeaters or introduce other deleterious effects. These effects aremore noticeable in two-wire circuits than in four-wire circuits.

The object of this invention is to provide means by which more accurateregulation or more uniformly distributed regulation can be obtainedwithout the necessity of placing a complete regulator installation ateach repeater station and avoiding at the same time, certaindisadvantages due to the possible oporation of several such independentregulators simultaneously. I accomplish this by providing means forchanging the gain at each repeater station, but controlling these meansby mechanism at the master station. It is highly desirable that the gaincontrol f devices at the various repeater stations of a given regulatorsection are operated in sequence, each repeaterthus being adjusted Iinstead of having the total change concentrated at one station. Theinvention comprises means, then, b which impulses are transmitted overan impulse circuit which will aflect the repeaters in sequence,introducing a gain or a loss, as may be determined by the condition ofthe pilot wire.

The invention. will be better understood by reference to theaccompanying drawings in which Figure 1 shows a circuit arrangementindicating the disposition of regulator sections and master regulatorstations. Fig. 2 shows a circuit arrangement by which the gains of therepeaters at various stations are controlled in sequence. Fig. 3 shows acircuit connection with the pilot channel or wire by which the impulses.are enerated which control the mechanism 0 Fig. 4 is a modified form ofimpulse genorator which also uses one pair of wires for both a pilotchannel and an impulse channel. Fig. 5 shows a further modification bywhich suitable impulses are transmitted to the various repeater stationsto control the gain Fig. 2.

of these repeaters and Fig. 6 is a detail of a part of the mechanism ofFig.5.

Referring more particularly to Fig. 1, there is shown a telephone linewith repeater stations A, B, C, etc. This, in general, is taken torepresent a pluralit of circuits such as may be enclosed in a cab e. Asection of this line comprising, for example, that portion whichincludes the repeaters A, B and C, is made one regulator section withone pair of wires 6 set aside as a pilot wire or channel, One of thestations, such as the tation B, is made a master station and is uppliedwith equipment 7 by which, as here inafter described, the gain of therepeaters A, B and C may be controlled. A similar pilot wire 8 withmaster controlling apparatus 9 is supplied for the section of the lineincluding the repeaters D, E and F, and so for other portions of theline.

The details of such regulating mechanism are given in greater detail inFig. 2 in which there is shown again the pilot wire 6 with mechanism 7,impulses from which are sent out in accordance with the condition of thepilot wire. ,These impulses travel out over a line 11, which, ingeneral, parallels the pilot wire 6. In the example to be described, itis assumed that there are three repeater stations to be controlled. Ateach of these repeater stations there will be inserted in the impulseline 11 adouble relay 12 12 or 1.2 which is adapted to operate mechanismsubstantially the same at each of the stations. I have shown thisapparatus in detail at one of the stations only, and, in particular, atthe middle one, which, in general, will be the master station.Associated with the relay windings 12 are two armatures 13 and 14.

The two relays are polar relays such that the armature 13 will be drawnup on a positive impulse passing throu h the windings 12 and thearmature 14 w1ll be drawn' up upon receipt of a negative impulse.Associated with the armatures 13 and 14 are two relays 18 and 19, thearmatures of which are arranged to step a ratchet wheel 20 in the onedirection or the other. This stepping arrangement, shown as a whole by Fis duplicated at stations A and C as shown at F and F Connected on theshaft of this ratchet wheel is a contact-making arm 22 which is adaptedto pass over a number of commutator segments 23 to 28, certain of whichare connected to relays 0a, b, c, and d, as will be hereinafterdescribed. Connectedto the contact arm 22 is atgrounded battery 29. Therelays a, b, 0, and d are arranged to control impedances, some of whichare in .impedances 34 and 35 across the line.

by H is duplicated at stations Aand C asshown at H, and H The operationof the circuit thus far described is as follows: If a positive impulsepasses over the line, the armature 13 is drawn up. This connects batteryto the relay 18, stepping ratchet Wheel 20 one step in the cloc wisedirection. This at the same time advances the contact arm 22 from theposition shown in the drawing by one step. position shown may be thatcorresponding to a normal gain for the repeater. Under these conditions,it will be observed that the relays b and c are operated, whereas therelays a and d are open. The closing of the relay 1) short-circuits theseries impedances 31 and 32, and the closing of the relay 0 connects theIn case it is desired to increase the gain of the repeater, it will bedesirable to increase the impedance of the shunt or decrease theimpedance of the series elements. Let us suppose that the temperatureconditionsof the line are such that it is desirable to increase the gainof the repeater by one unit corresponding, say, to one mile of gain intransmission. The drawing illustrates the case where this isaccomplished by causing the arm 22 to advance one step in the clockwisedirection. In this case the contact arm leaves the segment 23 and makescontact with the segment 24, retaining, however, its contact with thesegment 26. Under these circumstances, the relays a and d remain open.In addition the relay 0 is opened, so that the shunt across the input ofthe receiver is removed. In case gain of another mile in this regulatingsection is desired, it should be produced at one of the other repeaterstations, such as the station A. This is brought about by having thesame arrangement of apparatus at the station A as at B with thedifference, however, that the contact arm is displaced one step to theleft of that at the station B. The second step, then, of the ratchetwheel at each of the stations A, B and C will produce no effect at thestations B and C, but will produce an effect at station A in the samemanner as indicated for the previous step atthe station B. Still anotherain of one mile in transmission for the reguator section should beobtained by adjust ment at the station C, and a fourth gain of one mileshould be gained at the station E It will be observed that the fourthstep of the'contact arm 22 at the station B causes a transfer of contactfrom the segment 26 to the segment 27. Leaving the segment 26 opens therelay 1; and closes the relay 0:, which short-circuits the Whole seriesimped ance. A'fifth step would produce a similar effect at the stationA, and a sixth step would produce a similar effect at the station C.Provision obviously could be made for fur- The ther steps of the samekind by having a more complex arrangement of impedances 1n serles and inshunt to the line. 1

In case it is desired to reduce the gain, a negative impulse is sentover the impulse line, drawing up the armature 14. This operates therelay 19 to step the ratchet wheel and the contact arm 22 in acounterclockwise direction. The repeater at any one station is affectedonly every third step in the reverse order from that already described,and, after six negative impulses, conditions will be restored to thoseshown in Fig. 2. In case it is desired to further decrease the gain ofthe repeater, additional steps in the counterclockwise direction aretaken. It Wlll. be observed that the first step will produce an effectat the station C; the second step backward will produce an efiect at thestation A; and a third step backward Wlll produce an effect at thestation B. In making this last step, it will be observed that at thestation B the contact arm changes from the segment 26 to the segment 25.In this case the relay 5 is releasedand 0 alone remains closed. Underthese circumstances, the whole series resistance is in circuit and thewhole shunt impedance. In case further decrease in gain is desired,three steps more in the counterclockwise direction will cause thecontact arm 22 at B to change from segment 23 to 28, closing relay d andthereby decreasing the value of the shunt impedance. Similar effects areproduced at the stations A and C, the three operating in sequence In themanner indicated.

Fig. 3 shows the circuit arrangement for generating the impulses whichare to actuate the relays of the impulse circuit. While such circuitarrangements may take on a large variety of forms, I have shownspecificaly a Wheatstone bridge arrangement of which the pilot wireconstitutes one arm. Of the remaining arms. 41 and 42 will, in general,be fixed, and 45 will be variable to restore the bridge to balance.Across two corners of the bridge will be connected the battery 44 in theusual manner, and across the opposite two corners will be connected thegalvanometer G. The needle of this gal vanometer. acting as a relay,will connect a motor M with one or another of the batteries 47 and 48,depending upon the direction of the unbalance of the bridge, and thuscausing the motor M to rotate in the one direction or the other. Thismotor M carries a shaft with which there is associated a contact arm 49,sliding along the variable resistance 45 in such a way as to continuallytend to restore the balance of the bridge, and thus moving backwards andforwards in accordance with the fluctuations in the resistance of thepilot wire. The shaft of the motor also carries a contact arm 51, whichis adapted to make contact with two terminals 52 and 53 on a disc 54,this disc being so mounted as to be carried along in the one directionor the other by the contact arm 51 when it contacts with 52 or 53.Oppositely poled batteries 56 and 57 are connected with the terminas 53and 52 respectively, and a common terminal from the other side of thesetwo batteries connects with one wire of the conductors 10. the secondbeing connected with the contact arm 51. The relationship of the variousmembers associated with the shaft of the motor M is that shown in F ig.4, that portion of the shaft carrying the disc 54 and the arm 49 beingan extension of the shaft of the ratchet 20".

vThe operation of the apparatus of Fig. 3 is as follows: In case thereis a reduction in resistance of the pilot wire, the unbalance currentthrough the galvanometer causes connection of the motor, resulting in arotation of this motor in the direction to reduce the portion of theresistance 45 which is acting, that is, causing rotation of the contactarm 49 in the counterclockwise direction. This at the same time causescontact arm 51 to close with terminal 52, thus sending a positiveimpulse into conductors 10 which operates relay 19. Obviously a movementin the opposite direction would send out a negative impulse, and thusthe control of the gain of the various repeaters described in Fig. 2 iscontrolled by the conditions of the pilot wire.

Fig. 4 shows a modification of thearrangement thus far described, itbeing pro posed in this modification to use a single pair of wires, bothas a pilot channel and as an impulse channel. This figure shows the pairof wires 6, comprising the pilot channel and in this circuit areintroduced the relays which were formerly shown in the line 11. Thesereays and their armatures 13 and 14 operate apparatus which is the sameas that explained in connection with Fig. 2. The circuit differs,however, in the manner in which the impulses are originated. The pilotwire 6 is again made one arm ofa Wheatstone bridge to which there isconnected as before the galvanometer G, controlling the direction ofrotation of the motor M in the same manner as described above. The shaftofthis motor M. also as before, carries the contact arm which tendscontinually to restore the balance of the bridge. It also carries thecontact arm 51 and disc 54, by which positive or negative impulses aresent out from batteries 56 and 57. In this modification the impulses sosent out pass in series through two relays 58 and 59. Normally, currentfrom the battery 60 is passing through the relays in the pilot wire 6and the sending of signals consists in the interruption of this steadycurrent. This battery 60 is the one normally supplied for the bridge andis so arranged through relays that its tral position, a positive impulsewere to pass,

the armature would be raised to make con tact with the battery 61, thusoperating the relay 62. This, as will be seen from the figure, reversesthe battery connection to the bridge and also reverses the galvanometerconnection, so that the motion of the motor M is not affected by thereversal. As long as positive impulses are sent out through the contactarm 51, the connection of the bridge remains fixed. These same impulsespassing through the relay 59, which is associated with relays 64c and65, cause an intermittent operation of contacts of the relay 65, therebyinterrupting intermittently both the battery circuit 60 and thegalvanometer circuit and thus impulses are sent out over the line 6,which impulses may be spoken of as positive impulses and which willproduce operation of the armature 13 at the stations A, B and C toincrease the gain of the various repeaters in the manner hereinbeforedescribed. -Z l'a iti In case it is desired to decrease the gain of therepeaters, due to the COII'QSPOlldlIlg change in the resistance of thepilot wire 6, the motion of the motor M will be such as to send anegative impulse through the relays 58 and 59. This negative impulsethrough the relay 58 will cause a reversal of the battery andgalvanometer connections to the bridge by breaking the circuit of thebattery 61. These negative impulses will operate on the relay 59 in thesame manner as before to cause an intermittent interruption of thebattery and bridge connections by operation of the relay 65, thussending out the equivalent of an impulse over the line 6. This impulsewill, however, be in the opposite direction because of the reversal ofthe battery 60 and may therefore be spoken of as a negative impulse.This will therefore, operate the armature 14 and decrease the gain ofthe repeaters.

Still another modification for accomplishing the desired end is shown inFig. 5. Here, again, one pair of wires is used, both as a pilot channeland an impulse channel.

At the master station there is installed a making contact with one afteranother of the segments. Mounted adjacent to the disc is a sector member7 5, of sufiicient angular opening to cover SlX of the segments, the

sector being connected to ground. For simplicity I have shown in Fig. 5the various segments arranged linearly rather than circularly, thesector 75 being shown as a straight bar. During that part of therotation, when the brush is in contact with a grounded segment, therelay 71 will be operated. Under these conditions positive impulses frombattery 77 are transmitted over the pilot channel 6. In case therotating brush 70 is in contact with an of the other segments on thestationar isc, the relay 71 will not be operated an the armature makescontact with battery 78 to send negative impulses over the pilot channel6.

At each of the repeater stations there is installed a similar disc withcorresponding segments but without the sector 75. The brushes 70 on eachof these are caused to rotate in synchronism with the 'brush 70 at themaster station. Thus, when this brush 70 is in contact, as shown, withthe segment 6 of the master disc, it is in contact with the samesegments at the three repeater stations. With the discs at each of thesta tions there are associated four relays. At station A these areconnected respectively with segments 1, 4, 7 and 10, that is, with everythird segment. Similarly, at station B, the relays are associated withsegments 2, 5, 8 and 11 and at station C with segments 3, 6, 9 and 12.The armatures of these relays are included in circuit with relays a, b,a and d, which control the series and shunt impedances shown with thatportion of Fig. 2 designated as IL, and thus control the gain of therepeaters. The sector is controlled in .its position and caused torotate in one direction or the other by the motor, which in turn iscontrolledby the bridge of Fig. 3. As this shifts forward or backwards,then, a different group of segments of the master relay are grounded andthus either positive or negative impulses are transmitted to the line 6,causing corresponding operation of the armatures 13 and 1 1.

In addition to the twelve segments on the discs it will be desirable tohave certain segments which may be set aside for sending the necessaryimpulses to maintain synchronism between the rotating brushes at thevarious stations, and in the Fig. 6 I have shown two such segmentsmarked S, S, for this purpose.

Obviously, many modifications other than those described could bedevised for accomplishing the same purposeand I do not wish to belimited to the specific modifications disclosed, these being used forillustrative purposes only. i

i What is claimed is:

1. In a telephone transmission system, a telephone line, a plurality ofrepeater stations on said line and means at one station, responsive tovariations in the physical condition of the line, for varying therepeater gains at a plurality of the repeater stations.

2. In a telephone transmission system, a telephone line, a plurality ofrepeater stations on said line, means at each station for varying therepeater gain in any one of a plurality of degrees, and means at one ofsaid stations for controlling the first said means at the otherstations.

3. In a telephone transmission system, a telephone line, a plurality ofrepeater stations on said line and means at one station for varying therepeater gains at a plurality of the repeater stations in any one of aplurality of degrees.

4. In a telephone transmission system, a telephone line, a plurality ofrepeater'sta-. tions on said line, means at one station for varying therepeater gain at a plurality of the repeater stations, and means forcausing the stations to be afi'ected in sequence order.

5. In a telephone transmission system, a telephone line, a pilot channeladjacent thereto, a plurality of repeaters on said line,

means at each station for controlling the amplification in accordancewith the physical condition of the pilot channel and means at one ofsaid stations for controlling the first said means at the otherstations.

6. In a telephone transmission system, a telephone line, a pilot channeladjacent thereto, a plurality of repeaters on said line, means at eachstation for controlling the amplification in accordance with thephysical condition of the pilot channel, means at one of said stationsfor controlling the first said means at the other stations, and meansfor causing the stat-ions to be affected in sequence order.

7. In a telephone transmission system, a telephone line, a pilot channeladjacent thereto, a plurality of repeater stations on said line, meansat each of said stations for controlling the amplification and means atone of said stations, responsive to the physical'condition of the pilotchannel, for generating and transmitting impulses to the variousstations for controlling the first said means, the stations beingaffected in sequence order.

8. In a telephone transmission system, a telephone line, a plurality ofrepeater stations thereon, a plurality of pilot wires in succession andeach adjacent to a section of the line, means at each station forcontrolling the gain of the repeaters, the approximate mid-station ofeach section constituting a master station, means at each master stationassociated with and responsive to the condition of the line forcontrolling the first said means at each of the stations in its section.

9. In a telephone transmission system, comprising a telephone line withrepeaters and a pilot channel, the method of maintaining approximatelyconstant transmission level which consists in sending out impulses fromone repeater station in accordance with the physical condition of thepilot channel and controlling thereby the gain at the various repeaterstations.

10. In a telephone transmission system, comprising a telephone line withrepeaters and a pilot Wire, the method of maintaining approximatelyconstant ,transrnission level which consists in sending out impulsesfrom one repeater station in accordance with the physical condition ofthe pilot wire and controlling thereby the gain at the various repeaterstations, the stations being affected in sequence order.

In testimony whereof I have signed my name to this specification this24th day of August, 1922.

HARRY NYQUIST.

